1. Field of the Invention
This invention relates to a linear motion rolling guide unit in which a slider is moving relative to a rail.
2. Description of the Related Art
For a lubricating member and a slider used in such a type of linear motion rolling guide unit, FIG. 10 shows an example of the conventional structure, such as is disclosed in Japanese Patent Application No. 2007-073668 which has been filed by the present applicant. The conventional structure will be described below in detail with reference to FIG. 10.
FIG. 10 illustrates a casing 1 and end caps 2 which are respectively fixedly attached to the opposing ends of the casing 1. Endless circulation passages are provided inside the casing 1 and the end caps 2 for allowing a plurality of rolling elements such as rollers to endlessly circulate therein.
The casing 1 has a flat face 1a and a pair of side portions 1b which extend at right angles to the flat face 1a. As with the casing 1, each of the end caps 2 has a flat face 2a and a pair of side portions 2b which extend at right angles to the flat face 2a. In short, the entire slider S has a flat face and side portions which extend at right angles to the flat face. Endless circulation passages (not shown) are provided in the side portions to hold the rolling elements in such a way that the rolling elements can roll in the endless circulation passages.
The rolling elements are exposed on the mutually facing inner faces of the respective side portions 1b, where the rolling elements roll on the raceway faces of the rail, so that the slider S moves relative to the rail.
One of the end caps 2 (the right end cap 2 in the example in FIG. 10) has two opposing end faces, one end face making contact with the casing 1 and the other end face facing the outside. An end-face seal 3, which is a separate member from the end cap 2, is fixedly attached to this outward-facing face of the end cap 2. The end-face seal 3 comprises a lip 3a making contact with the raceway face of the rail (see the left end-face seal 3), preventing the entry of dust and the like into the slider S sliding on the rail.
Likewise, the outward-facing face of the other end cap 2 (the left end cap 2 in the example in FIG. 10) is also provided with an end-face seal 3. In this case, however, a lubricating member a is interposed between the end-face seal 3 and the end cap 2.
The lubricating member a comprises a member body 4, a plate 5 fixed to one end face of a member body 4, an oil packing 6 fixed to the other end face of the member body 4, and a case 7 housing the member body 4, the plate 5 and the oil packing 6.
The member body 4 is formed, for example, by pressurizing and molding a synthetic resin and oil in one piece or alternatively by molding a granular synthetic resin and then impregnating it with a lubricant, which is a resin-made member with fine open cells which are produced in the molding process and can hold a lubricant such as oil.
Similar to the casing 1 and the end cap 2, the member body 4 also has a coupling portion 4a and a pair of side portions 4b respectively extending out from the opposing sides of the coupling portion 4a in a direction at right angles. The side portions 4b respectively have mutually facing faces from which arc-shaped contact lubrication portions 4c respectively protrude. The contact lubricating portions 4c maintain a dimensional relationship to the rail that ensures that the contact lubricating portions 4c are in light contact with the raceway faces on the rail side faces when the slider S is straddlingly mounted on the rail.
The coupling portion 4a of the member body 4 is depressed in one face oriented in the sliding direction of the slider S to form a recessed embedding portion 8. The embedding portion 8 is formed of a rectangular cross-section recess extending between the opposing side portions 4b. An impregnation holding member 9 is embedded in the embedding portion 8.
The impregnation holding member 9 is formed of materials capable of being impregnated with a lubricant, such as a felt material. The impregnation holding member 9 has a larger oil-impregnation space per unit volume, that is, a greater amount of lubricant per unit volume than the member body 4 does.
However, it is necessary that the force sucking the lubricant into the impregnation holding member 9 is equal to or smaller than that into the member body 4. The force sucking the lubricant referred to here means the strength of sucking the lubricant into the impregnation holding member 9 or the member body 4 by capillary action or surface tension. In either case, the relationship between the sucking forces in the impregnation holding member 9 and the member body 4 is required to be a relationship such that the lubricant seeps from the impregnation holding member 9 into the member body 4.
After the impregnation holding member 9 is secured in the embedding portion 8 of the member body 4, an oil packing 6 is placed over the face of the member body 4 so as to seal the open end of the embedding portion 8. The oil packing 6 is formed in a shape approximately covering the face (facing in the sliding direction of the slider S) of the member body 4 except for the contact lubricating portion 4c. The oil packing 6 has a feed hole 6a which is a small-diameter hole formed in a position corresponding to the embedding portion 8, so that the embedding portion 8 communicates with the outside through the feed hole 6a. 
The member body 4 and the oil packing 6 are mounted in the case 7. The case 7 is formed in a shape covering the outer periphery of the oil packing 6 and the member body 4. The case 7 has a through hole 7a drilled in alignment with the feed hole 6a of the oil packing 6 when the oil packing 6 is mounted in the case 7.
The plate 5 is a metallic member, which is placed on the face of the member body 4 opposite to the face on which the oil packing 6 is placed. That is, the member body 4 and the oil packing 6 are sandwiched between the case 7 and the plate 5, and all their faces, except for the mutual facing faces of the pair of side portions 4b, are covered with the case 7 and the plate 5.
The lubricating member a structured as described above is fixedly attached to the casing 1 of the slider S through screws N while the plate 5 is in contact with the end cap 2. At this stage, the end face seal 3 is simultaneously secured to the face of the case 7 which is opposite to the plate 5 secured to the end cap 2.
The end face seal 3, which is secured to the case 7, has an insertion hole 3b drilled in a position aligned with the feed hole 6a and the through hole 7a. Thus, the embedding portion 8 formed in the member body 4 communicates with the outside through the feed hole 6a of the oil packing 6, the through hole 7a of the case 7 and the insertion hole 3b of the end face seal 3.
The slider S with the lubricating member a secured to one of the end caps 2 moves relative to the rail while the contact lubricating portions 4c of the lubricating member a are in contact with the raceway faces of the rail. The lubricant impregnating the member body 4 is supplied from the contact lubricating portion 4c onto the raceway faces of the rail to lubricate the raceway faces.
As the lubricant is supplied from the contact lubricating portions 4c onto the raceway faces in this manner, the amount of the lubricant in the member body 4 gradually decreases. However, upon the decrease in the lubricant from the member body 4, the lubricant exuded from the impregnation holding member 9 gradually seeps into the member body 4.
Since the impregnation holding member 9 has a larger amount of lubricant held per unit volume than that held in the member body 4 as described earlier, although the impregnation holding member 9 has a smaller volume than the member body 4 has, the impregnation holding member 9 is capable of fully supplying the amount of lubricant consumed by the member body 4.
As additional lubricant is fed from the impregnation holding member 9 to the member body 4, the lubricant in the impregnation holding member 9 gradually decreases. However, the lubricating member a is capable of refilling the impregnation holding member 9 with lubricant as described below.
The embedding portion 8 provided in the member body 4 is linked to the outer face of the end face seal 3 through the feed hole 6a, the through hole 7a and the insertion hole 3b. 
Then, an injector 10 holding liquid lubricant such as oil is inserted from the end face seal 3 such that the leading end of the injector 10 passes through the feed hole 6a. At this stage, the liquid lubricant is supplied to the impregnation holding member 9 embedded in the embedding portion 8, thereby storing up liquid lubricant in the impregnation holding member 9, which then makes it possible to feed the lubricant to the member body 4 again.
The rail slidably carrying the slider S as described above is not limited to being laid on a horizontal surface at all times. The rail may be laid on a vertical surface such as a wall or on a ceiling. For example, when the rail is fixedly attached to a vertical surface to extend horizontally, one of the side portions 1b of the slider S straddling the rail is located at a higher level and the other side portion 1b is located at a lower level. In other words, the two side portions are respectively situated in an upper position and a lower position relative to the vertical surface. If the side portions of the slider S are respectively disposed above and below in this manner, the embedding portion 8 is vertically oriented.
If the embedding portion 8 is situated in a vertical position, the lubricant filling the embedding portion 8 or the lubricant impregnating the impregnation holding member 9 unevenly accumulates in the lower-level part of the embedding portion 8. As a result, the side portion 4b located at a higher level lacks lubricant, giving rise to the impossibility of uniform lubrication. Also, when the rail is laid on a tilted surface or a ceiling, a similar situation occurs.
In addition, if lubricant is unevenly distributed as described above, this causes a shortened effective period of the lubricating capability. That is, the required amount of lubricant may become substantially insufficient within a short period.